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Operator NameDescriptionTime KPressing a single key or button Skilled typist (55 wpm) Average typist (40 wpm) User unfamiliar with the keyboard Pressing shift or control key 0.35 (average) 0.22 0.28 1.20 0.08 PP1PP1 Pointing with a mouse or other device to a target on a display Clicking the mouse or similar device 1.10 0.20 HHoming hands on the keyboard or other device 0.40 DDraw a line using a mouseVariable depending on the length of line MMentally prepare to do something (e.g. make a decision) 1.35 R (t)System response time – counted only if it causes the user to wait when carrying out their task t Keystroke-level model